Molecular adaptive convergence in the α-globin gene in subterranean octodontid rodents

Tuco-tucos (Ctenomys) and related coruros (Spalacopus) are South American subterranean rodents. An energetically demanding lifestyle within the hypoxic/hypercapnic underground atmosphere may change the selective regime on genes involved in O₂ transport in blood. In addition, some species of tuco-tucos may be found at high altitude, thus facing additional reductions in changes O₂ availabily. We examined sequence variation in the alpha globin subunit gene of hemoglobine in these lineages, within a robust phylogenetic context. Using different approaches (classical and Bayesian maximum likelihood (PAML/Datamonkey) and alternatives methods (TreeSAAP)) we found at least 2 sites with evidence of positive selection in the basal branch of Octodontidae, but not in tuco-tucos. These results suggest some adaptive changes associated to fossoriality, but not strictly to life underground.